Low noise, low dropout voltage regulator
First Claim
1. A low dropout (LDO) voltage regulator comprising:
- a scaling amplifier for receiving a bandgap voltage, Vbg, and outputting a scaled Vbg,a reference MOSFET device for reducing the scaled Vbg by a voltage Vgs formed across gate and source nodes of the reference MOSFET device to form a reduced level of the scaled Vbg,an RC network for filtering the reduced level of the scaled Vbg and outputting a filtered voltage, andan output buffer for receiving and increasing the filtered voltage by the voltage Vgs to recover the scaled Vbg,where the scaled Vbg is used as a regulated voltage output, andthe RC network is coupled between the reference MOSFET device and the output buffer.
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Abstract
A low dropout (LDO) voltage regulator includes a scaling amplifier for receiving a bandgap voltage, Vbg, and outputting a scaled Vbg. A reference MOSFET device is included for reducing the scaled Vbg by a first voltage Vgs formed across gate and source nodes of the reference MOSFET device. This forms a reduced level of the scaled Vbg. An RC network filters the reduced level of the scaled Vbg and outputs a filtered voltage. An output buffer is included for receiving and increasing the filtered voltage by a second voltage Vgs in order to recover the scaled Vbg. The scaled Vbg is used as the desired regulated voltage output. The second voltage Vgs, which is produced by the output buffer, is equal to the first voltage Vgs, which is produced by the reference MOSFET device.
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Citations
20 Claims
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1. A low dropout (LDO) voltage regulator comprising:
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a scaling amplifier for receiving a bandgap voltage, Vbg, and outputting a scaled Vbg, a reference MOSFET device for reducing the scaled Vbg by a voltage Vgs formed across gate and source nodes of the reference MOSFET device to form a reduced level of the scaled Vbg, an RC network for filtering the reduced level of the scaled Vbg and outputting a filtered voltage, and an output buffer for receiving and increasing the filtered voltage by the voltage Vgs to recover the scaled Vbg, where the scaled Vbg is used as a regulated voltage output, and the RC network is coupled between the reference MOSFET device and the output buffer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A voltage regulator for providing a regulated voltage output comprising:
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an RC network disposed between an operational amplifier and an output buffer, in which the operational amplifier receives a bandgap voltage and outputs a scaled bandgap voltage as the regulated voltage output, the RC network filters a portion of the scaled bandgap voltage and outputs a filtered voltage, and the output buffer modifies the filtered voltage to recover the scaled bandgap voltage as the regulated voltage output. - View Dependent Claims (15, 16, 17, 18, 19)
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20. A method of providing a regulated voltage output comprising the steps of:
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scaling an input voltage to provide a scaled bandgap voltage; reducing the scaled bandgap voltage by a predetermined amount to output a reduced voltage; filtering the reduced voltage to output a filtered voltage; after filtering, restoring the scaled bandgap voltage, based on the predetermined amount; and outputting the restored scaled bandgap voltage as the regulated voltage output, wherein reducing the scaled bandgap voltage is performed by a reference MOSFET device;
outputting the restored scaled bandgap voltage is performed by an output buffer; and
filtering is performed by an RC network; andthe RC network is coupled between the reference MOSFET device and the output buffer.
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Specification